1. Field of the Invention
The present invention concerns a disturbance estimated-type control system, a gas compressor control system and a method of designing a disturbance estimated type control system and, in particular, relates to a disturbance estimated type control system and a gas compressor control system that are insensitive to parameter variations, such as a heat load variation and rotating speed change, and to a method of designing the disturbance estimated type control system.
2. Description of the Related Art
Displacement control of a refrigeration air conditioning system for a car air conditioner is for observing an air temperature at an outlet of an evaporator or a room temperature by a temperature sensor and changing a displacement of a gas compressor such that the observed temperature coincides with a target temperature set in advance.
Alternatively, the displacement of the gas compressor is changed such that a refrigerant suction pressure of the gas compressor becomes a desired pressure value. For example, in Japanese Patent No. 1746774, displacement control is performed using rotating speed information of a gas compressor together with air temperature information.
An overall schematic configuration view of the air conditioning system is shown in FIG. 12. The air conditioning system is mounted, for example, on a car. In FIG. 12, an evaporator 51 is a heat exchanger involving ventilation by a fan 52 and cools air in a cabin. Refrigerant gas that is evaporated within the evaporator 51 is taken into a variable displacement type gas compressor 10 and pressurized to be sent to a condenser 53.
In the condenser 53, the refrigerant gas is liquidized and heat absorbed from the inside of the cabin is discharged to the outside of the car. An expansion valve 54 is made to rapidly decrease a pressure of the refrigerant gas from a high pressure to a low pressure. A rotating shaft 11 of the variable displacement type gas compressor 10 is made such that a shaft power of an engine 59 is transmitted to it and it is rotationally driven.
A sectional view of the variable displacement type gas compressor 10 is shown in FIG. 13 and a sectional view cut along line A—A and viewed in the direction of arrows A in FIG. 13 of the variable displacement type gas compressor 10 is shown in FIG. 14.
A suction port 1 of the variable displacement type gas compressor 10 is made to suction refrigerant gas from the evaporator 51 connected to the outside.
A cylinder 3 is clamped between a front head 5 and a rear side block 7. A rotor 9 is rotatably arranged within the cylinder 3.
The rotor 9 is penetrated by and fixed to a rotary shaft 11. Bane grooves 13 are formed in the radial direction on the external circumference of the rotor 9 and banes 15 are slidably inserted in the bane grooves 13. Then, the banes 15 are biased to the internal wall of the cylinder 3 by a centrifugal force and an oil pressure of the bottoms of the bane grooves 13 when the rotor 9 is rotating.
The inside of the cylinder 3 is partitioned into a plurality of small chambers by the rotor 9 and the banes 15. These small chambers are referred to as compressing chambers 17, which repeat increasing and decreasing changes of a displacement by the rotation of the rotor 9.
Then, when the rotor 9 rotates to change the displacement of the compressing chambers 17 in this way, low-pressure refrigerant gas is taken in from the suction port 1 and compressed by the displacement change. A case 19 is fixed in the peripheral end portion of the cylinder 3 and the rear side block 7 and a discharge chamber 21 is formed inside this case 19.
High-pressure refrigerant gas compressed in the compressing chamber 17 is sent to the discharge chamber 21 via a discharge port 23 and a discharge valve 25. Then, the refrigerant gas is sent to the condenser 53 in the outside from the discharge chamber 21 via the discharge port 27.
This variable displacement type gas compressor 10 is provided with a displacement varying mechanism 30. This displacement varying mechanism 30 is made such that it can variably adjust a discharge capacity of refrigerant gas according to a temperature in a cabin. An example of a configuration of the displacement varying mechanism 30 is shown in FIG. 15.
A control plate 29 is arranged in the front head 5 to face the side portion of the cylinder 3. Notches 29a are provided in two parts of the control plate 29. These notches 29a cause the inside of the cylinder 3 and a suction chamber 31 leading to the suction port 1 to communicate with each other. On the other hand, the compressing chambers 17 are formed in spaces closed by the part on the control plate 29 where there is no notch, the internal wall of the cylinder 3 and the banes 15.
When the control plate 29 is rotated to the right, the notches 29a are rotated in the right direction, whereby the positions where the compressing chambers 17 are formed also move to the right side and the displacement of the compressing chambers 17 at this point is also reduced. In this way, a discharge capacity is adjustable by rotating the control plate 29.
The rotation of the control plate 29 is performed by a driving shaft 39 of hydraulic drive via a pin 33. Oil is injected into a sleeve 35 from the discharge chamber 21 by adjusting the opening degree of a control valve 37 and the driving shaft 39 is moved straight by oil pressure at this point. Then, this straight movement is converted into rotating movement via the pin 33 to cause the control plate 29 to rotate.
An injection amount of oil can be changed by altering the opening degree of the control valve 37. This alteration of the opening degree is performed by changing a displacement control command value (duty ratio) shown in FIG. 16.
The control plate 29 is rotated under the balance with an elastic force by a spring 38 in accordance with a differential pressure between a control pressure Pc in the sleeve 35 and a pressure Ps in the suction chamber 31.
Further, in FIG. 12, for example, in order to detect an air temperature at the outlet of the evaporator 51, a temperature sensor 55 is disposed. In addition, in order to detect a rotating speed of the engine 59, a rotating speed sensor 57 is disposed.
Then, a displacement control command value is calculated in a control circuit 61 based on a detected signal of this temperature sensor 55 and a rotating speed of the engine 59. This displacement control command value is signal-amplified by a displacement control signal generating circuit 65 and, then, transmitted to the control valve 37 of the displacement varying mechanism 30.
Next, a control method of this displacement varying mechanism 30 will be described based on a flow chart of FIG. 17.
For simplicity, description will be made with the case in which a displacement of the variable displacement type gas compressor 10 is reduced such as the case in which a rotating speed of the engine 59 is increased as an example.
Now, the case in which a detected temperature at the outlet of the evaporator 51 has become lower than a target temperature 67 at the outlet of the evaporator 51 is assumed. In this case, in order to prevent the inside of the cabin from being cooled excessively, it is necessary to lower cooling capability.
First, in step 1 (it is abbreviated as S1 in the figure and the same is true for subsequent steps), a target refrigerant flow rate of the variable displacement type gas compressor 10 is calculated based on a temperature deviation between a target temperature and a detected temperature. The calculation in this case is performed by PID control or the like. Next, in step 3, a rotating speed of the variable displacement type gas compressor 10 is calculated from this calculated target refrigerant flow rate or a discharge capacity of the variable displacement type gas compressor 10 is calculated taking a rotating speed of the engine 59 into account.
In step 5, a rotating speed correcting calculation is performed from this discharge capacity based on a not-shown property curve showing a relation between a discharge capacity and a displacement control command value and a displacement control command value by which an opening degree of the control valve 37 should be adjusted is determined. The displacement control command value at this point is commanded to be small. As a result, an average current falls in step 7 and the opening degree of the control valve 37 is reduced in step 9.
At this point, the control pressure Pc inside the sleeve 35 falls in step 11. Thus, the driving shaft 39 is moved downward in step 13 and the control plate 29 rotates to the right in step 15. As a result, the discharge capacity of the variable displacement type gas compressor 10 becomes small in step 17 and the cooling capability falls.
In addition, other than the above-described control method, methods such as a method of preparing a plurality of control modes and switching among the modes and a method of altering a model based on observation information and changing a parameter of a compensator according the model alteration have been used because the air conditioning system has different physical property depending on a heat load variation and a difference of an operation condition and also has strong nonlinearity (Japanese Patent Nos. 2090676 and 2086982).
However, the embodiment according to Japanese Patent No. 1746774 increases the number of sensors because a rotating speed sensor is required. In addition, even if an existing rotating speed sensor is used, there is a disadvantage in that the number of communication means increases. Thus, although a technology for realizing equivalent or higher control performance even without rotating speed information is necessary, the realization has been difficult conventionally.
On the other hand, in the case of Japanese Patents Nos. 2090676 and 2086982, providing a plurality of control compensators leads to increase of development load. In addition, alteration of a compensator is likely to cause trouble in practical use because there arise problems in that the number of sensors is increased, development load is increased and the compensator itself becomes complex.
The present invention has been devised in view of such conventional problems and it is an object of the present invention to provide a disturbance estimated type control system and a gas compressor control system that are insensitive to parameter variations, such as a heat load variation and a rotating speed change, and to a method of designing a disturbance estimated type control system.